Multi-electrode lead

ABSTRACT

A multi-electrode lead ( 10 ) comprises an elongate carrier ( 12 ) having a longitudinal axis. A plurality of electrical conductors is carried by the carrier ( 12 ), a plurality of electrodes being connected in spaced relationship to each conductor. The electrodes ( 14 ) are arranged at axially spaced intervals along the carrier ( 12 ) so that, along the length of the carrier ( 12 ) electrode ( 14 ) associated with any one of the conductors only once has an electrode ( 14 ) associated with another one of the conduct adjacent to that any one electrode ( 14 ). In another aspect of the invention, an ablating device ( 50 ) comprises an elongate tubular sleeve ( 52 ) for effecting spot ablation of tissue, a sensing electrode catheter being receivable in the passage ( 54 ) of the sleeve for assisting in positioning of the ablating electrode ( 56 ), in use Preferably, the sensing electrode catheter is the multi-electrode lead ( 10 ) of the first aspect of the invention.

FIELD OF THE INVENTION

This invention relates to a multi-electrode lead. More particularly, theinvention relates to a multi-electrode lead for use in medicalapplications for sensing predetermined parameters, such as, for example,electrical activity, temperature, or the like.

BACKGROUND OF THE INVENTION

Electrodes are used in the medical field for applications such asstimulation, sensing, ablation and defibrillation.

Typically, such a lead is in the form of a catheter which is insertedthrough a blood vessel of a patient's body to the desired location inthe patient's body.

The thinner the electrical lead, the easier it is to insert andmanipulate. Further, by making the lead thinner, the patient suffersless discomfort.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided amulti-electrode lead which comprises:

an elongate carrier having a longitudinal axis; and

a plurality of electrical conductors carried by the carrier, a pluralityof electrodes being connected in spaced relationship to each conductor,the electrodes being arranged at axially spaced intervals along thecarrier so that, along the length of the carrier, any one electrodeassociated with any one of the conductors only once has an electrodeassociated with another one of the conductors adjacent to said any oneelectrode.

In this specification, unless the context clearly indicates otherwise,the term “adjacent” is to be understood to mean that one electrode isnext to, but spaced from, its neighbouring electrode.

In a preferred embodiment of the invention, the carrier comprises amandrel about which the conductors are carried, for example, by beinghelically wound around the mandrel.

The mandrel is, preferably, a tubular mandrel to form a lumen of thelead. The mandrel may be a flexible, plastics tube.

A covering of a non-conductive material may be applied about theconductors to cover the conductors.

The electrodes may be formed by elements of electrically conductivematerial applied to an outer surface of the covering. The material fromwhich the elements are made may be a biocompatible metal such as, forexample, platinum.

Each element may be in the form of a band or annulus arranged about thecarrier. A first of the electrodes may be arranged at a distal end ofthe carrier.

In one embodiment of the invention, at least at that region of thecarrier having the electrodes, the covering may be of a porous material.Where the coating is of a porous material, the metal may be appliedabout the coating to permeate through the pores of the coating to makecontact with the conductors.

Instead, in another embodiment of the invention, the coating may beremoved at regions where it is desired to form electrodes to expose theconductors at that region with the metal forming the elements being indirect electrical contact with their associated conductors.

In yet another embodiment of the invention, each electrode may bedefined by a region of the conductor exposed by the removal of thecovering at that region, with or without a conductive element applied tothe exposed region.

According to a second aspect of the invention, there is provided anablating device, the ablating device comprising:

an elongate, tubular sleeve defining an open passage; and

an ablating electrode carried at a distal end of the sleeve foreffecting spot ablation of tissue, a sensing electrode catheter beingreceivable in the passage of the sleeve for assisting in positioning ofthe ablating electrode, in use.

In a preferred form of the invention, the ablating device is used incombination with the multi-electrode lead as described above where, bypositioning the sleeve over the electrodes of the lead, appropriatepositioning of the ablating electrode of the device can be achieved. Itwill be appreciated that, as the ablating device passes over and coversthe electrodes of the multi-electrode lead, the signals from the coveredelectrodes become attenuated. As a result, a clinician is able tomonitor the progress of the of the ablating device relative to the lead.Therefore, the sensing electrode catheter may be the multi-electrodelead as described above.

Accordingly, a third aspect of the invention provides an ablatingassembly which includes, in combination,

a multi-electrode lead, as described above; and

an ablating device, also as described above.

According to a fourth aspect of the invention, there is provided amethod of monitoring a predetermined parameter in a patient, the methodcomprising the steps of:

inserting a multi-electrode lead, as described above, through a bodyvessel of the patient;

placing the electrodes of the multi-electrode lead at a desired site inthe patient;

monitoring the parameter at at least certain of the electrodes; and

processing signals received from the electrodes for determining a valueof the parameter.

Where the parameter being monitored is abnormal electrical activity, themethod may include processing the signals by, in respect of eachconductor, summing the signals received from the electrodes connected tothat conductor, at least one of the received signals beingrepresentative of normal electrical activity. The method may theninclude determining a time delay resulting from spatial separation ofthe electrodes of that conductor. Still further, the method may includesubtracting the signals which reflect normal electrical activity.

Where the parameter being monitored is temperature, the method mayinclude monitoring the temperature at the site using a first electrodeof the lead which is arranged closest to the site. The method may theninclude also monitoring the temperature at a position remote from thesite by using a second electrode to give a reference, body temperature.Still further, the method may include subtracting the temperaturemonitored by the second electrode from the temperature monitored by thefirst electrode to give an indication of the temperature at the site.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described by way of example with reference to theaccompanying drawings in which:

FIG. 1 shows a side view of a multi-electrode lead, in accordance with afirst aspect of the invention;

FIG. 2 shows a schematic, side view of an ablating assembly, inaccordance with a third aspect of the invention, the assembly includingan ablating device, in accordance with a second aspect of the invention;

FIG. 3 shows a schematic, sectional end view of the lead; and

FIG. 4 shows a set of graphs indicating, in a simplified manner, theoperation of the lead of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring initially to FIG. 1 of the drawings, a multi-electrode lead inthe form of a catheter 10, in accordance with a first aspect of theinvention, is illustrated and is designated generally by the referencenumeral 10. The catheter 10 includes an elongate, tubular carrier 12having a proximal end 12.1 and a distal end 12.2 and defining alongitudinal axis.

A plurality of electrodes 14 is arranged at axially spaced intervalsabout an outer periphery of the carrier 12, proximate the distal end12.2 of the tubular carrier 12.

The carrier 12 supports a plurality of conductors. Although not shown inFIG. 1 of the drawings, a cross-sectional view of the catheter 10 isshown in FIG. 3 of the drawings. The catheter 10 has the tubular carrier12 defining a lumen 16. The electrodes 14, as described above, arecarried about an outer periphery of the tubular carrier 12. In theformation of the catheter 10, an inner, tubular mandrel 18 is provided.A plurality of conductors 22 are arranged about the mandrel 18 and alayer or coating 24 of an electrically insulating material is appliedabout the mandrel 18 with the conductors 22 being embedded in the layer24.

Each electrode 14 is electrically connected to one of the conductors 22.Each conductor 22 has more than one electrode 14 connected to it ataxially spaced intervals along the length of the carrier 12.

To connect one of the electrodes 14 to its associated conductor 22, thematerial 24 at the relevant location of the carrier 12 is removed toexpose the conductor 22. When the metal used to form the electrode 14 isapplied, by appropriate deposition techniques, the metal is brought intoelectrical contact with the relevant conductor 22 to connect theelectrode 14 to that conductor 22. As illustrated in FIG. 3 of thedrawings, the electrodes 14 are annular or band-shaped and extend aboutan outer circumference of the carrier 12.

As described above, each conductor 22 has more than one electrode 14connected to it. In the example illustrated, the catheter 10 containsfive conductors 22. One of the conductors 22A has three electrodes 14associated with it as illustrated in FIGS. 1 and 2 of the drawings whileeach of the remaining conductors, 22B-22E, has two electrodes 14associated with it.

The electrodes 14 are arranged along the carrier 12 such that any oneelectrode 14 associated with any one of the conductors 22 only once hasan electrode 14 associated with another one of the conductors 22adjacent to it. For example, as illustrated in FIG. 1 of the drawings,electrode 14.1 is connected to conductor 22A.

Electrode 14.2 is connected to conductor 22B, electrode 14.3 isconnected to conductor 22C, electrode 14.4 is connected to conductor 22Dand electrode 14.5 is connected to 35 conductor 22E. The followingelectrode, electrode 14.6, is then, again, connected to conductor 22Aand the next electrode 14.7 is connected to conductor 22C and so on. Thebenefit of this arrangement is that a large number of electrodes, inthis case, eleven electrodes, can be arranged on the catheter 10 butwith the catheter 10 having fewer conductors 22. This makes the catheter10 of smaller diameter than would otherwise be the case making it moreeasily manoeuvrable within blood vessels of the patient. The patient'sbody can act as the return electrode for each of the electrodes 14.

The catheter 10 is used for sensing one of a number of parameters of apatient's body. For example, the catheter 10 can be used in sensingabnormal electrical activity in the heart or brain of a patient. Formonitoring cardiac activity, this is achieved by inserting the catheter10 via a patient's femoral vein to the desired location in the patient'sheart. The electrodes 14 of the catheter 10 are used for monitoring orsensing electrical activity in pulmonary veins of the patient. Theelectrical activity is sensed by the electrodes 14 and return signalsare sent from the electrodes 14 to a control device (not shown). Thereturn signal from each electrode 14 is monitored to decide whichelectrode 14 is sensing the highest level of abnormal electricalactivity. If, for example, the signals on conductors 22B and 22C carrythe signals indicating abnormal electrical activity, that would be anindication that the abnormal electrical activity took place at, orbetween, electrodes 14.2 and 14.3. By appropriate signal processing, itcan be determined at which electrode 14 the highest level of abnormalelectrical activity occurred.

Referring to FIG. 4 of the drawings a simplified version of the mannerof determining where the highest level of abnormal electrical activityoccurred is shown. For example, in graph 30, a pulse 32 is detected byelectrode 14.2 and is conveyed along conductor 22B to the control unit.A further pulse 34 would be monitored by electrode 14.9, which is alsoconnected to conductor 22B, as shown in graph 36. This pulse 34 istemporally spaced with respect to pulse 32. What is received at thecontrol box on conductor 22B is, as shown in graph 38, a pulse 40 whichis the sum of the pulses 32 and 34. The control box can determine, dueto the smaller amplitude of the pulse 34, that it represents normalelectrical activity. By filtering out or subtracting this pulse 34, thepulse 32 remains which is representative of abnormal electrical activityat electrode 14.2. Appropriate remedial action can then be taken.

Referring now to FIG. 2 of the drawings, an ablating assembly, inaccordance with a third aspect of the invention, is illustrated and isdesignated generally by the reference numeral 50. This assembly 50incorporates the catheter 10 as described above with reference to FIG. 1of the drawings. An ablating device 20, in accordance with a secondaspect of the invention, comprising a sleeve 52 is received over thelead 10. The sleeve 52 has a passage 54 of sufficiently large diameterto accommodate the catheter 10. An ablating electrode 56 is arranged ata distal end of the sleeve 52 and a pulley arrangement, using wires 57is used to position the sleeve 52 relative to the catheter 10.

Using the example described above, assuming the abnormal electricalactivity is determined as having occurred at or adjacent electrode 14.2then, while the catheter 10 remains in situ, the catheter 10 is receivedin the passage 54 of the ablating sleeve 52. The sleeve 52 is manoeuvredalong the catheter 10 so that the ablating electrode 56 overlies theelectrode 14.2. An ablating pulse is sent down the sleeve 52 to ablatetissue adjacent the electrode 14.2 to create a lesion. The lesioninhibits the continued abnormal electrical activity at that site.

When the catheter 10 is used for measuring temperature, the arrangementis slightly different in that, unlike when electrical activity is beingsensed, a return lead is required. Accordingly, a return wire (notshown) for a thermocouple is included. This return wire is also embeddedin the layer 24 of the carrier 12.

In sensing temperature, if ablation is to occur at, or adjacent, theelectrode 14.2 then, using the ablating electrode 56 of the assembly 50,the temperature at that electrode 14.2 is monitored together with thetemperature another electrode remote from electrode 14.2, for example,electrode 14.9. The temperatures of the monitored electrodes 14.2 and14.9 are summed. It is reasonable to assume that the temperature atelectrode 14.9, because it is remote from the ablation site, is at bodytemperature. Therefore, when the temperature monitored by the electrode14.9 is subtracted from the summed temperatures of electrodes 14.2 and14.9, the remaining temperature is an indication of the temperature atelectrode 14.2 and this can be monitored to inhibit overheating of thesite.

Referring again to FIG. 3 of the drawings, a benefit of having theconductors 22 embedded in the layer 24 is that the lumen 16 of thetubular carrier 12 is free to allow other pieces of equipment (notshown), for example, a steering mechanism, a lasso, a conduit for acooling solution, or the like, to pass through the lumen 16.

Accordingly, it is an advantage of the invention that a multi-electrodelead, or catheter, is provided which is far thinner than othermulti-electrode leads of which the applicant is aware. Also, themulti-electrode lead can be used for sensing various differentparameters of the patient's body such as electrical activity,temperature, or the like. Due to the fact that the lumen of the lead orcatheter is unobstructed by conductors, the lumen can be used for otherpurposes such as a steering mechanism, a shape forming member, theintroduction of a cooling solution, or the like.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

1. A multi-electrode lead which comprises: an elongate carrier having alongitudinal axis; and a plurality of electrical conductors carried bythe carrier, a plurality of electrodes being connected in spacedrelationship to each conductor, the electrodes being arranged at axiallyspaced intervals along the carrier so that, along the length of thecarrier, any one electrode associated with any one of the conductorsonly once has an electrode associated with another one of the conductorsadjacent to said any one electrode.
 2. The lead of claim 1 in which thecarrier comprises a mandrel about which the conductors are carried. 3.The lead of claim 2 in which the mandrel is a tubular mandrel to form alumen of the lead.
 4. The lead of claim 1 further comprising a coveringof a non-conductive material is applied about the conductors to coverthe conductors.
 5. The lead of claim 4 in which the electrodes areformed by elements of electrically conductive material applied to anouter surface of the covering.
 6. The lead of claim 5 in which thematerial from which the elements are made is a biocompatible metal. 7.The lead of claim 6 in which each element is in the form of a band orannulus arranged about the carrier.
 8. The lead of claim 7 in which, atleast at that region of the carrier having the electrodes, the coveringis of a porous material.
 9. The lead of claim 8 in which, where thecoating is of a porous material, the metal is applied about the coatingto permeate through the pores of the coating to make contact with theconductors.
 10. The lead of claim 6 in which the coating is removed atregions where it is desired to form electrodes to expose the conductorsat that region with the metal forming the elements being in directelectrical contact with their associated conductors.
 11. The lead ofclaim 1 further comprising a covering of non-conductive material appliedabout the conductors to cover the conductors and in which each electrodeis defined by a region of the conductor exposed by the removal of thecovering at that region.
 12. A method of monitoring a predeterminedparameter in a patient, the method comprising the stePs of: inserting amulti-electrode lead, as claimed in claim 1, through a body vessel ofthe patient; placing the electrodes of the multi-electrode lead at adesired site in the patient; monitoring the parameter at at leastcertain of the electrodes; and processing signals received from theelectrodes for determining a value of the parameter.
 13. The method ofclaim 12 which includes, where the parameter being monitored is abnormalelectrical activity, further comprising the steps of processing thesignals by, in respect of each conductor, summing the signals receivedfrom the electrodes connected to that conductor, at least one of thereceived signals being representative of normal electrical activity. 14.The method of claim 13 which includes determining a time delay resultingfrom spatial separation of the electrodes of that conductor.
 15. Themethod of claim 14 which includes subtracting the signals which reflectnormal electrical activity.
 16. The method of claim 12 which includes,where the parameter being monitored is temperature, further comprisingthe steps of monitoring the temperature at the site using a firstelectrode of the lead which is arranged closest to the site.
 17. Themethod of claim 16 which includes also monitoring the temperature at aposition remote from the site by using a second electrode to give areference, body temperature.
 18. The method of claim 17 which includessubtracting the temperature monitored by the second electrode from thetemperature monitored by the first electrode to give an indication ofthe temperature at the site.